A clamping device for clamping a fastener, such as for example a bolt, is generally attached to an electrical wrench or a manual wrench. Currently, the common clamping device has various mechanisms for mating with the fasteners having different sizes. However, with regard to the various types of known clamping devices, when in use, on one hand, they are inconvenient to carry, and on the other hand, it is oftentimes difficult for the common user to know how to choose and/or use the appropriate clamping device.
For example, international patent application publication number WO2009132426 describes an adjustable clamping device, wherein the clamping device can clamp bolts with various sizes. However, such a clamping device has a relatively complex structure with large overall size, and the manufacturing cost is high.